1. Field of the Invention
The invention relates in general to the button control technology, and more particularly to a power saving method for a scan type keyboard.
2. Related Art
With the progress of the technology, the electronic technology has been developed from the earliest vacuum tubes and transistors to the integrated circuit chips, which have been widely used. Thus, electronic products have gradually become indispensable necessities in the daily life of the modern human beings. Many articles have been gradually electrized for the purpose of facilitating the convenience in using them.
Many control methods of the electronic products, such as computers, mobile phones and the like, often adopt the button control. Generally speaking, the methods of detecting the scanning of the keyboard buttons are classified into two kinds. The first kind is a matrix-type scan, and the second kind is a triangular-type scan. FIG. 1 is a schematic illustration showing the circuit of a conventional matrix-type scan keyboard. In this example, 5×5 keyboard keys will be illustrated. The circuit includes a matrix-type scan keyboard controller 100, five horizontal scan lines HS10 to HS14, and five vertical scan lines VS10 to VS14. The matrix-type scan keyboard controller 100 includes ten I/O pins I/O-10 to I/O-19.
When the keyboard button detection starts, the I/O pins I/O-10 to I/O-14 of the horizontal scan lines HS10 to HS14 are controlled to sequentially output scan pulses, and the I/O pins I/O-15 to I/O-19 of the vertical scan lines VS10 to VS14 are controlled to perform the detection. When the I/O pin I/O-10 outputs the scan pulse and the user presses a button 101, the horizontal scan line HS10 and the vertical scan line VS13 are short-circuited. Thus, the scan pulse is received by the I/O pin I/O-18. At this time, the matrix-type scan keyboard controller 100 can assert that the button 101 has been pressed.
FIG. 2 is a schematic illustration showing the circuit of a conventional triangular-type scan keyboard. Referring to FIG. 2, the circuit includes a triangular-type scan keyboard controller 200, nine vertical scan lines VS20 to VS28 and ten horizontal scan lines HS20 to HS29. Similarly, the triangular-type scan keyboard controller 200 includes ten I/O pins I/O-20 to I/O-29. When the keyboard button detection starts, the I/O pins I/O-20 to I/O-29 of the horizontal scan lines HS20 to HS29 are controlled to sequentially output the scan pulses. More particularly, when one of the I/O pins I/O-20 to I/O-29 outputs the scan pulse, the other remaining I/O pins I/O-20 to I/O-29 are used for detecting. For example, when the I/O pin I/O-20 outputs the scan pulse, the I/O pins I/O-21 to I/O-29 are used for detecting. Similarly, if the I/O pin I/O-21 outputs the scan pulse and a button 201 is pressed, the vertical scan line VS21 and the horizontal scan line HS24 are short-circuited. Thus, the scan pulse is received by the I/O pin I/O-24. The triangular-type scan keyboard controller 200 can assert that the button 201 has been pressed.
Compared FIG. 1 with FIG. 2, it is obtained that the triangular-type scan keyboard controller 200 having ten I/O pins can control 45 buttons, while the matrix-type scan keyboard controller 100 having ten I/O pins can control 25 buttons. In other words, under the consideration of the input/output (I/O) resources of the integrated circuit (IC), it is hoped to achieve more button control with the fewer I/O resources, and the control of the triangular-type scan keyboard can solve this problem.
The advantage of the matrix-type scan keyboard will be described in the following. When the matrix-type scan keyboard enters the sleep mode, as shown in FIG. 1, the I/O pins I/O-10 to I/O-14 are set to the logic high voltages, while the I/O pins I/O-15 to I/O-19 are set to the logic low voltages, and a register is used to record the logic states of the I/O pins I/O-15 to I/O-19. When the user presses any button, the logic high voltages of the I/O pins I/O-10 to I/O-14 are transferred to the I/O pins I/O-15 to I/O-19 such that the logic states of the I/O pins I/O-15 to I/O-19 are changed to wake up the matrix-type scan keyboard. Because the power consumption of the sleep mode is extremely low, it is suitable for the system with the low current consumption, such as a remote controller and the like.
However, the consumed current for the triangular-type scan keyboard control chip typically ranges from several hundreds of uA to several mA, which is still acceptable with respect to the system with the high current consumption. However, it is difficult for the triangular-type scan keyboard control chip to achieve this condition that the sleep current of the remote controller is limited to several uA. Thus, the triangular-type scan keyboard cannot be easily accepted by the user or the manufacturer.